DK161404B

DK161404B - Vapor generator with a temperature controlled regulator

Info

Publication number: DK161404B
Application number: DK113186A
Authority: DK
Inventors: Hermann Brueckner; Lothar Stadie; Franz Lankes
Original assignee: Siemens Ag
Priority date: 1985-03-16
Filing date: 1986-03-12
Publication date: 1991-07-01
Also published as: FI84201B; DK113186A; FI84201C; ES553030A0; EP0195298B1; DE3509637A1; JPS61213504A; DE3667097D1; ES8708048A1; FI860864A; ATE48184T1; YU33486A; FI860864A0; DK113186D0; DK161404C; EP0195298A1

Abstract

1. Steam generator having a temperature-regulated parallel pipe system with injection coolers (12, 13) which are connected upstream of the end heating surfaces (7, 8, 9, 10) of the individual lines (3, 4, 5, 6) of the parallel pipe system, having a measuring sensor (39) for the temperature of the mixed steam downstream of the parallel pipe system, said sensor being connected to the steam collecting line (11) which accomodates the individual lines, and having a regulating device for the injection coolers, which device is controlled by the measuring sensor and a desired value input, there being associated with each of the lines (3 to 6) which are connected in parallel a separate temperature measuring sensor (37, 38) for the steam temperature, said temperature measuring sensors being connected to a temperature regulator (40) which controllably opens the injection cooler (12, 13) of the line with the highest steam temperature and controllably closes the injection cooler (12, 13) of the line with the lowest steam temperature, there being associated with the hot ends of the individual parallel pipes (17 to 26) of each line (3 to 6) separate temperature measuring sensors (27 to 36) which are connected to a monitoring logic system (42, 43) which determines the measured value with the highest temperature and compares it with a fixedly preset reference value (44, 45) for the temperature and controllably opens the associated injection cooler (12, 13) when the reference value is exceeded, with priority over other control commands.

Description

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Opfindelsen angår en dampgenerator med et temperaturreguleret parallelrørsystem med foran slutvarmefladerne i de enkelte strenge i parallel rørsystemet, med en måleføler for temperaturen af blandingsdampen efter parallel rørsystemet, som er tilsluttet til dampsaml eledningen, 5 som rummer de enkelte strenge, og med en af måleføleren og af en referenceværdigiver styret reguleringsindretning til indsprøjtningskølerne, hvor der til hver af de parallelt koblede strenge hører separate temperaturmål efølere til damptemperaturen, og hvor disse temperaturmålefølere er tilsluttet til en temperaturregulator, som åbner indsprøjtnings-10 køleren i strengen med den højeste damptemperatur og lukker indsprøjtningskøleren i strengen med den laveste damptemperatur.The invention relates to a steam generator having a temperature controlled parallel pipe system with the front end heat surfaces of the individual strings in the parallel pipe system, with a measurement sensor for the temperature of the mixing steam according to the parallel pipe system, which is connected to the steam collection line, which contains the individual strings, and with one of the measuring sensors and of a reference value controlled control device for the injection coolers, where each of the parallel coupled strings belongs to separate temperature gauges for the steam temperature, and where these temperature measuring sensors are connected to a temperature controller which opens the injection cooler in the string with the highest steam temperature and closes the string with the lowest vapor temperature.

En sådan dampgenerator er kendt fra DE-A-1 816 851.Such a steam generator is known from DE-A-1 816 851.

Ved målefølere med parallel rørsystemer er det til temperaturregulering af dampen kendt at anbringe en indsprøjtningskøler foran slut-15 varmefladerne på højtrykoverhederen og mellem overhederen. Styreventilerne til indsprøjtningskøleren styres til dette formål via en regulator, som atter påvirkes af en i dampsaml eledningen anbragt temperaturføler, samt af en referenceværdigiver. Ved parallel rørsystemer, dvs. ved varmeflader med indbyrdes parallelt koblede rørbundter, skotter el-20 ler membranvægge kan uensartede opvarmningstilstande og forskellige gennemstrømningshastigheder i rørledningerne ikke undgås. Det fører til, at der mellem de indbyrdes parallelle rørledninger og strenge kan optræde utilladeligt høje temperaturdifferencer, som fører til utilladeligt høje materialespændinger, og at der lokalt, afhængigt af drif-25 ten, også kan opnås utilladeligt store absoluttemperaturer i de enkelte rør i parallel rørsystemet. Sådanne overbelastninger fører så til rørskader med forøgede reparationsomkostninger til følge og en mindsket rådighed over dampgeneratoranlægget.In the case of measuring sensors with parallel pipe systems, it is known for temperature control of the steam to place an injection cooler in front of the final heating surfaces on the high pressure superheater and between the superheater. For this purpose, the control valves for the injection cooler are controlled via a regulator, which is again actuated by a temperature sensor located in the steam collection line and by a reference value sensor. In parallel pipe systems, ie. In the case of heating surfaces with interconnected pipelines, bulkheads or membrane walls, different heating conditions and different flow rates in the pipelines cannot be avoided. As a result, there may be unacceptably high temperature differences between the mutually parallel pipelines and strings, which lead to unacceptably high material stresses, and, in addition, depending on the operation, unacceptably large absolute temperatures can be achieved in the individual pipes in parallel. pipework. Such overloads then lead to pipe damage resulting in increased repair costs and a reduced availability of the steam generator system.

Til undgåelse af sådanne overbelastninger er det allerede kendt at 30 begrænse damptemperaturen opadtil. Til dette formål må man finde sig i en vis forringelse af total virkningsgraden af dampgeneratoren.To avoid such overloads, it is already known to limit the vapor temperature upwards. For this purpose, one must find some deterioration in the total efficiency of the steam generator.

Fra DE-A-1 776 137 er det allerede kendt ved gennemstrømningsdampgeneratorer med to parallelle strenge at udstyre hver af disse to strenge med en indsprøjtningskøler og at drive disse indsprøjtningskø-35 lere med en indsprøjtningsmængde på 2 - 3 %. Ved uens belastning af - 2 -From DE-A-1 776 137 it is already known in the case of flow steam generators with two parallel strings to equip each of these two strings with an injection cooler and to operate these injection coolers with an injection rate of 2-3%. At different loads of - 2 -

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strengene skal disse to indsprøjtningskølere styres i modfase. Med denne udformning af en gennemstrømningsdampgenerator kan en uensartet belastning af de to strenge udmærket reguleres. Trods dette kan lokale overbelastninger alligevel opstå i de enkelte rør i en og samme streng, 5 der fx. opstår strømningsbetinget ved lokalt forandret dampbiæredannelse, som gør det tilrådeligt at drive kedlen ikke alt for nær ved den teoretisk kakulerbare maximumeffekt.these two injection coolers must be controlled in the counter phase. With this design of a flow steam generator, a uniform load of the two strings can be very well regulated. Nevertheless, local overloads can nevertheless occur in the individual pipes in one and the same string, 5 e.g. The flow condition arises from locally altered vapor barrier formation, which makes it advisable not to operate the boiler too close to the theoretically cachable maximum power.

Til grund for opfindelsen ligger derfor den opgave at anvise en måde, hvorpå overbelastninger af enkelte rør eller strenge kan undgås i 10 dampgeneratorer med parallel rørsystemer, uden at damptemperaturen skal sænkes for meget i forhold til den teoretisk tilladte damptemperatur.Therefore, the object of the invention is to provide a way in which overloads of individual pipes or strings can be avoided in 10 steam generators with parallel pipe systems without lowering the steam temperature in relation to the theoretically permissible steam temperature.

Opgaven løses ved hjælp af ejendommelighederne i krav 1. Hensigtsmæssige videreudformninger beskrives i kravene 2-6.The task is solved using the properties of claim 1. Appropriate further designs are described in claims 2-6.

Som følge af tilknytningen af en separat strengmåleføler for damp-15 temperaturen til hver enkelt af de parallelt koblede strenge konstateres dels uens belastninger i de enkelte strenge og dels tilvejebringes samtidig en forudsætning for at aflaste den stærkest belastede streng via en styrelogik ved styring af den tilhørende indsprøjtningskøler og ved styring af den til den mindst belastede streng hørende indsprøjt-20 ningskøler at tilvejebringe en udligning. Derved udjævnes belastningen af de enkelte strenge, som fx. membranvægge, skotter og bestemte rørbundter. På basis af denne udligning af belastningerne af de enkelte strenge opnås en endnu mere pålidelig sikring mod overbelastning henholdsvis overtemperatur, hvis der til de varme ender på de enkelte pa-25 rail el rør i ^ver enkelt streng knyttes separate temperaturmålere, som er tilsluttet en overvågningslogik, som bestemmer måleværdien med den højeste temperatur og sammenligner den med en fast, på forhånd indgivet referenceværdi for temperaturen og styrer den tilhørende indsprøjtningskøler ved overskridelse af referenceværdien forud for andre styre-30 kommandoer. Herved undgås effektivt en lokal overbelastning eller overophedning, uden at den totale ydelse af dampgeneratoren skal sænkes væsentligt. Det vil sige, at totalydelsen af dampgeneratoren kan føres nærmere til den teoretiske maximumbelatning.As a result of the connection of a separate strain gauge sensor for the steam temperature to each of the parallel coupled strings, both different loads are determined in the individual strings and partly at the same time a prerequisite for relieving the strongest loaded string via a control logic by controlling the associated injection cooler and by providing the injection load cooler associated with the least strained string to provide an equalizer. This will equalize the load on the individual strings, which e.g. diaphragm walls, bulkheads and specific tubular bundles On the basis of this equalization of the loads of the individual strings, an even more reliable protection against overload or over-temperature is obtained, if separate temperature gauges connected to a single strand are connected to the hot ends of the individual pipe or pipe in a single strand. monitoring logic which determines the measurement value with the highest temperature and compares it with a fixed pre-set reference value for the temperature and controls the associated injection cooler by exceeding the reference value prior to other control commands. This effectively avoids a local overload or overheating without significantly reducing the total output of the steam generator. That is, the total performance of the steam generator can be brought closer to the theoretical maximum load.

Yderligere enkeltheder ved opfindelsen forklares nærmere ved hjælp 35 af et på figuren vist udførelseseksempel.Further details of the invention are explained in greater detail by means of an exemplary embodiment shown in the figure.

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Figuren viser et skematisk koblingsdiagram for en dampgenerator med et parallel rørsystem og kredsløbet til regulering af temperaturen i de enkelte varmeflader.The figure shows a schematic circuit diagram of a steam generator with a parallel pipe system and the circuit for regulating the temperature of the individual heating surfaces.

Ved den på figuren skematisk viste dampgenerator 1 strømmer føde-5 vandet nedefra via den her ikke viste economiser og fordamper ind i en fordelerledning 2 og derfra ind i den til diverse parallelt koblede strenge 3, 4, 5 og 6 tilsluttede for- og siutoverhedervarmeflader 7, 8, 9, 10 i dampgeneratoren. Disse varmeflader kan være dele af kedelydervæggen eller også dele af en mellem- eller membranvæg. I gengivelsen på 10 fig. 1 fører den venstre streng 3 ind i en del af ydervæggen 7 på en dampgenerator 1 og den højre streng 4 ind i en mellemvæg 9 i dampgeneratoren, og her er de i den højre og den venstre streng 3, 4 indtegnede, øvre varmeflader 8, 10 slutoverhedervarmeflader, dvs. rørbundter, som man må forestille sig installeret omtrent midt i røggastrækket. Bag 15 siutovervarmefladerne 8, 10 udmunder de enkelte strenge i en dampsamle-ledning 11, som fører til forbrugeren, i almindelighed til dampturbinen (ikke vist).At the steam generator 1 shown schematically in the figure, the feed water flows from below via the economizer not shown here and evaporates into a distribution line 2 and from there into the pre- and siutor superheater heat connected to various parallel wires 3, 4, 5 and 6. , 8, 9, 10 in the steam generator. These heating surfaces may be parts of the boiler sound wall or also parts of an intermediate or diaphragm wall. In the representation of FIG. 1, the left strand 3 enters a portion of the outer wall 7 of a steam generator 1 and the right strand 4 into an intermediate wall 9 of the steam generator, and here are the upper heating surfaces 8 shown in the right and the left string 3, 4; 10 end superheater heating surfaces, ie. pipe bundles, which you can imagine installed approximately in the middle of the flue gas line. Behind the 15 superheated heating surfaces 8, 10, the individual strands of a steam collector conduit 11 leading to the consumer generally lead to the steam turbine (not shown).

I hver af de to viste strenge 3, 4 ser man efter varmefladerne 7, 9 1 kedelydervæggen henholdsvis mellemvæggen de til den tilhørende 20 slutoverheder hørende varmeflade 8, 10 en indsprøjtningskøler 12, 13, som hver via en separat, motorstyret ventil 14, 15 er tilsluttet til fødevandsledningen 16. Både i de varme ender af parallel rørene 17 - 26 i den enkelte slutoverheder 8, 10 samt i de fra den pågældende slutoverheder udgående, enkelte strenge 3-6 samt i samledampledningen 25 11, i hvilken strengene til slut munder ind, er der anbragt temperatur-målefølere 27 - 39. De i dem fra slutoverhederen 8, 10 udgående strenge indbyggede temperaturmålefølere 37, 38 er tilsluttet til en temperaturregulator 40, som på sin side atter via en yderligere styrelogik 41 er forbundet med indstillingsmotorerne for de enkelte styreventiler 14, 15 30 til indsprøjtningskølerne 12, 13. Temperaturregulatoren er konstrueret således, at den i på forhånd givne tidsintervaller aftaster temperatur-målefølerne 37, 38 med henholdsvis den højeste og den laveste damptemperatur og styreventilen 14, 15 til indsprøjtningskølerne 12, 13 i strengen 3-6 med den højeste damptemperatur lidt yderligere op og 35 lukker styreventilen 14, 15 i indsprøjtningskøleren 12, 13 i strengen 3 - 4 -In each of the two strings 3, 4, the heating surfaces 7, 9 1 and the boiler sound wall, respectively, the heating surface 8, 10 of the associated 20 final units, 10, 10 are injected, each of which is via a separate motor controlled valve 14, 15. connected to the feed water line 16. Both at the hot ends of the parallel pipes 17 - 26 in the individual end authorities 8, 10 as well as in the individual strings exiting from the end authorities, single strands 3-6 and in the joint steam line 25 11, in which the strings finally open , temperature measuring sensors 27 - 39 are arranged. The temperature measuring sensors 37, 38 which extend from the final units 8, 10 are connected to a temperature controller 40, which in turn is connected again via an additional control logic 41 to the setting motors for the individual control valves 14, 15 for the injection coolers 12, 13. The temperature controller is designed so that the temp at the predetermined time intervals senses the temp. the eratur measurement sensors 37, 38 with the highest and lowest vapor temperatures respectively and the control valve 14, 15 for the injector coolers 12, 13 in the string 3-6 with the highest vapor temperature slightly further open and 35 the control valve 14, 15 in the injector cooler 12, 13 in the string 3 - 4 -

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- 6 med den laveste damptemperatur lidt til. Temperaturerne i de enkelte strenge til nærmes således til hinanden.- 6 with the lowest vapor temperature slightly. The temperatures in the individual strings are thus approached.

Temperaturmålefølerne 27 - 36 i parallel rørene 17 - 26 i de enkelte slutoverhedere 8, 10 er hver tilsluttet en overvågningsi ogik 42, 43 5 for hver slutoverheder, der på forhånd givne tidsintervaller aflæser dem. Måleværdierne sammenlignes med en på forhånd given referenceværdi 44, 45 i et komparatortrin 46, 47. Overskrider en måleværdi referenceværdien, dannes der i komparatortrinnet et signal, som dels via en negation 48 - 51 og en ELLER-funktion 52 - 55 blokerer overførslen af 10 signaler fra temperaturregulatoren 40, og dels åbner styreventilen 14, 15 til indsprøjtningskøleren 12, 13 i den tilhørende streng 3-6.The temperature measurement sensors 27 - 36 in the parallel tubes 17 - 26 in the individual final superheaters 8, 10 are each connected to a monitoring signal 42, 435 for each final superheater that reads them at predetermined intervals of time. The measured values are compared with a predetermined reference value 44, 45 in a comparator stage 46, 47. If a measured value exceeds the reference value, in the comparator stage a signal is generated which partly via a negation 48 - 51 and an OR function 52 - 55 blocks the transmission of 10 signals from the temperature controller 40, and partly open the control valve 14, 15 to the injector cooler 12, 13 in the associated string 3-6.

Den i dampsaml eledningen 11 værende måleføler 39 for dampblandingstemperaturen er tilsluttet et reguleringsled 56, som sammenligner denne måleværdi med en forud fastsat værdi 57, i hvilken den af forbru-15 geren ønskede damptemperatur afspejler sig. Afhængigt af om måleværdien ligger over eller under denne tilsigtede værdi frembringes en styrekommando til åbning eller lukning. Denne måleværdi indføres via en ELLER-port 58, 59 til styreledningerne for alle styreventiler 14, 15 for indsprøjtningskøleren 12, 13. På den anden indgang til denne ELLER-port 20 58, 59 til hver af styreventilerne kan der være tilført et af stillingen i styreventilen afhængigt signal, som ved ekstremsti 11 ingen for den tilhørende styreventil udebliver og således forhindrer en overstyring af samme.The steam mixing temperature measurement sensor 39 in the steam mix line 11 is connected to a control link 56 which compares this measurement value to a predetermined value 57 in which the steam temperature desired by the consumer is reflected. Depending on whether the measurement value is above or below this intended value, an opening or closing control command is generated. This measurement value is applied via an OR gate 58, 59 to the control lines for all control valves 14, 15 for the injection cooler 12, 13. On the second input to this OR gate 20 58, 59 to each of the control valves, one of the positions in the the control valve dependent signal which, at extreme path 11, does not appear for the associated control valve and thus prevents over-control of the same.

Ved drift af dampgeneratoren 1 trykkes fødevandet via en her ikke 25 yderligere vist fødevandspumpe, en economiser og en fordamper på gengivelsen i figuren nedefra via fordelerledningen 2 ind i de enkelte indbyrdes parallelle strenge 3 - 6, og de i disse strenge indbyggede for-og siutoverhedervarmeflader 7 - 10. I disse opvarmes fødevandet i forskellige parallel rør og samles derpå påny og varmes i parallel rørene 30 17 - 26 i de yderligere siutoverhedervarmeflader 8 - 10 til den ønskede sluttilstand. Dampen samles i de tilhørende strenge 3-6. Hver af disse parallelt koblede varmeflader eller strenge leder derpå dampen ind i samledampledningen 11, som leder den overhedede damp til forbrugeren, i almindelighed en dampturbine.In operation of the steam generator 1, the feed water is pressurized via a feed water pump, an economizer and an evaporator shown below, via the distribution line 2 into the individual parallel strands 3 - 6, and the pre- and siut superheater heating surfaces incorporated in these strings. 7-10. In these, the feed water is heated in various parallel tubes and then re-collected and heated in the parallel tubes 30 17-26 in the additional siutor superheater heating surfaces 8-10 to the desired final state. The steam is collected in the corresponding strings 3-6. Each of these parallel coupled heating surfaces or strands then directs the steam into the collector steam line 11, which conducts the superheated steam to the consumer, generally a steam turbine.

35 Som følge af uensartetheder i varmeafgivelsen og som følge af dy- - 5 -35 As a result of differences in heat dissipation and as a result of -

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namiske uensartetheder i strømningsmodstanden 1 de enkelte parallel rør - således som de fx. kan opstå som følge af for tidlig fordampning -opstår der i de parallelle rør lokalt og tidsmæssigt forskellige rør-og damptemperaturer. Disse temperaturer konstateres atter af de til de 5 enkelte strenge 3-6 tilsluttede temperaturfølere. De foranlediger, at temperaturregulatoren 40 åbner den til den varmeste streng hørende sky-deventil lidt og lukker den til den koldeste streng hørende styreventil yderligere. Som følge af disse med korte tidsintervaller foretagne reguleringer sker der en udligning af varmeeffekten i de forskellige 10 strenge, og der undgås temperaturskævheder og materialeoverbelastninger især i stationær drift. Til det af temperaturføleren 39 i dampsamleled-ningen 11 styrede reguleringsled 56 reduceres derved reguleringsstrækningen til et enkeltstrenget system, således at alle styreventiler til denne hovedregulering kun behøver at blive stillet parallelt. Dette kan 15 ske uafhængigt af den pågældende åbningsposition for de enkelte styreventiler i indsprøjtningskøleren. Kun ved slutstilling undertrykkes styrekommandoerne til reguleringsleddet 56, der ville føre til en over-skridning af denne slutstilling. De hertil hørende modsat rettede kommandoer ledes gennem som følge af opdelingen i en lukkende signalvej 20 60, 61 og en åbnende signalvej 62, 63 og mellemkoblingen af ELLER-por-tene 64 - 67. Disse ELLER-porte styrer koblingselementer 68 - 71, som ligger 1 strømkredsen for indstillingsmotorerne for styreventilerne.namic disparities in the flow resistance 1 the individual parallel tubes - such as those e.g. can occur as a result of premature evaporation - in the parallel pipes local and temporally different pipe and vapor temperatures occur. These temperatures are again determined by the temperature sensors connected to the 5 single strings 3-6. They cause the temperature controller 40 to open the sliding valve belonging to the hottest string slightly and to close the coldest string control valve further. Due to these adjustments made at short intervals, the heat effect is equalized in the various 10 strings, and temperature distortions and material overloads are avoided especially in stationary operation. The control link 56 controlled by the temperature sensor 39 in the vapor conduit line 11 is thereby reduced to a single-stranded system, so that all control valves for this main control need only be set in parallel. This can be done independently of the respective opening position of the individual control valves in the injection cooler. Only at the end position is the control commands of the control link 56 suppressed which would lead to an overrun of this end position. The associated opposite commands are passed through as a result of the division into a closing signal path 20 60, 61 and an opening signal path 62, 63, and the interconnection of the OR gates 64 - 67. These OR gates control coupling elements 68 - 71 which is located 1 the circuit of the setting motors for the control valves.

Uafhængigt heraf forhindres det ved hjælp af overvågningslogikken 42, 43 at enkelte parallelrør i varmefladerne i slutoverhederen eller 25 mellemoverhederen kan blive overbelastet. Dette sker ved en blokering af signal overførslen fra temperaturregulatoren og fra reguleringsleddet i lukkeretningen ved samtidig åbning af styreventilen i den tilhørende 1ndsprøjtn1ngskøler.Independently of this, it is prevented by the monitoring logic 42, 43 that single parallel tubes in the heating surfaces of the final or intermediate superheater can be overloaded. This is done by blocking the signal transmission from the temperature regulator and from the regulating link in the closing direction by simultaneously opening the control valve in the corresponding injection spray cooler.

Denne form for temperaturregulering ved dampgeneratoren kan på 30 analog måde anvendes også til mellemoverhedervarmeflader foran mellem-og lavtryktrinnet i en dampturbine. Den tillader, at dampgeneratoren drives nærmere sin teoretisk netop tilladelige effektovergrænse, uden at der skal frygtes en lokal eller tidsmæssig utilladelig termisk belastning.This type of temperature control at the steam generator can also be used in an analogous manner to medium superheater heating surfaces ahead of the intermediate and low pressure stages of a steam turbine. It allows the steam generator to be driven closer to its theoretically just permissible power limit, without the fear of a local or temporally impermissible thermal load.

35 Herved opnås der en højere effekt og en højere virkningsgrad for dampgeneratoren.35 This provides a higher power and a higher efficiency for the steam generator.

Claims

1. A steam generator with a temperature controlled parallel pipe system with injection coolers (12, 13) inserted in front of the air heater surfaces (7, 8, 9, 10) of the individual strings (3, 4, 5, 6) of the parallel pipe system, with a measuring sensor (39) for the temperature of the mixing steam according to the parallel electric pipe system, which is connected to the steam collection line (11), which accommodates the individual strings, and controlled by a measuring sensor and a reference value regulator for the injection coolers, where each of the parallel coupled strings (3 - 6), separate temperature measurement sensors (37, 38) belong to the steam temperature, and where these temperature measurement sensors are connected to a temperature controller (40) which opens the injector cooler (12, 13) in the string with the highest vapor temperature and closes the injection cooler (12, 13) in the string with the lowest vapor temperature, characterized in that to the hot ends of the individual parallel pipes (17 - 26) in each string (3 - 15) 6) associate separate temperature gauges (27 - 36) connected to a monitoring logic (42, 43) which record the measurement value with the highest temperature, compare it with a fixed, preset reference value (44, 45) for the temperature and open it associated injection cooler (12, 13) by exceeding the reference value prior to other control commands.

Temperature control according to claim 1, characterized in that the signals from the temperature target connected to the steam collection line (11) (39) by means of the control link open or close all injection coolers (12, 13), synchronously but with lower priority in 25 conditions. to the other control signals.

Temperature control according to claim 1, characterized in that the injection coolers (12, 13) can be operated via control valves (14, 15).

Temperature control according to claim 1, characterized in that the control valves (14, 15) can be opened and closed stepwise via control pulses.

Temperature control according to claim 1, characterized in that the control signals in the monitoring logic (42, 43) block the commands from the temperature controller (40) via a negation and one in the control path of the control logic. 55) and opens the control valve (14, 15) to the injection cooler (12, 13).

Temperature control according to claim 1, characterized in that the temperature sensors (27 - 36) are connected only to a few representative parallel pipes (17 - 26) from each heating surface (8 - 10). 10